Impostors: integrate into 3ner

1 files changed, 49 insertions, 102 deletions

diff --git a/impostor.cginc b/impostor.cginc
index 4236778..1d5c9b5 100644
--- a/impostor.cginc
+++ b/impostor.cginc
@@ -2,19 +2,10 @@
 #define __IMPOSTOR_INC
 
 #include "UnityCG.cginc"
+#include "globals.cginc"
 #include "vertex_deformation.hlsl"
 
-SamplerState bilinear_clamp_s;
-Texture2D _ImpostorAtlas;
-float4 _ImpostorAtlas_TexelSize;
-int _GridResolution;
-float _Cutoff;
-float _SphereRadius;
-float3 _ImpostorMainCameraPos;
-
-float4 _Color;
-float _DebugMode;
-
+// Utility functions for hemispherical octahedral mapping
 float2 HemiOctEncode(float3 N) {
     N.y = max(N.y, 1e-4);
     float3 p = hemi_octahedron_to_plane(normalize(N), 0, float3(1,0,0), float3(0,1,0), 1);
@@ -40,27 +31,7 @@ float3 DirFromCell(float2 cell, float gridRes) {
     return HemiOctDecode(uv);
 }
 
-float2 ClampUvInCell(float2 uv) {
-    uv = saturate(uv);
-    float2 halfTexelInCell = 0.5 * _ImpostorAtlas_TexelSize.xy * (float)_GridResolution;
-    return clamp(uv, halfTexelInCell, 1.0 - halfTexelInCell);
-}
-
-float4 SampleAtlasGrad(float2 uv, float2 cell, float2 uvGradX, float2 uvGradY) {
-    uv = ClampUvInCell(uv);
-
-    float invGridRes = rcp((float)_GridResolution);
-    float2 atlasUv = (cell + uv) * invGridRes;
-
-    // Important: gradients must be computed in-cell; do not let integer cell offsets affect mip selection.
-    return _ImpostorAtlas.SampleGrad(bilinear_clamp_s, atlasUv, uvGradX * invGridRes, uvGradY * invGridRes);
-}
-
-// Branchless barycentric weights in a unit square split into two triangles along the (0,0)-(1,1) diagonal.
-// Returns weights for the 4 square corners:
-//   .x = (0,0), .y = (0,1), .z = (1,0), .w = (1,1)
-// Only three weights are non-zero for any point (true barycentric within one triangle),
-// but sampling both possible "middle" vertices avoids triangle-selection discontinuities.
+// Branchless barycentric weights in a unit square split into two triangles
 float4 GridCellBarycentric4(float2 p) {
     float w00 = 1.0 - max(p.x, p.y);
     float w11 = min(p.x, p.y);
@@ -86,40 +57,43 @@ float2 VirtualPlaneUV(float3 frameDir, float3 pivotToCam, float3 vertexToCam) {
     return uv * -1.0 + 0.5;
 }
 
-struct appdata {
-    float4 vertex : POSITION;
-    UNITY_VERTEX_INPUT_INSTANCE_ID
-#ifdef IMPOSTOR_SHADOW_PASS
-    float3 normal : NORMAL;
-#endif
-};
+// General purpose ray-sphere intersection
+bool RaySphereIntersect(float3 ro, float3 rayDir, float3 origin, float radius) {
+    float3 originToRo = ro - origin;
+    float b = dot(originToRo, rayDir);
+    float c = dot(originToRo, originToRo) - radius * radius;
+    return (b * b - c) >= 0.0;
+}
 
-struct v2f {
-#ifdef IMPOSTOR_SHADOW_PASS
-    V2F_SHADOW_CASTER;
-#else
-    float4 pos : SV_POSITION;
-    UNITY_FOG_COORDS(7)
-#endif
-    float3 worldPos : TEXCOORD1;
-    float3 centerPos : TEXCOORD2;
-    UNITY_VERTEX_OUTPUT_STEREO
-};
+#if defined(_IMPOSTORS)
+
+float2 ClampUvInCell(float2 uv) {
+    uv = saturate(uv);
+    float2 halfTexelInCell = 0.5 * _Impostors_Atlas_TexelSize.xy * (float)_Impostors_Grid_Resolution;
+    return clamp(uv, halfTexelInCell, 1.0 - halfTexelInCell);
+}
+
+float4 SampleAtlasGrad(float2 uv, float2 cell, float2 uvGradX, float2 uvGradY) {
+    uv = ClampUvInCell(uv);
 
-v2f vert(appdata v) {
-    v2f o;
-    UNITY_SETUP_INSTANCE_ID(v);
-    UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
+    float invGridRes = rcp((float)_Impostors_Grid_Resolution);
+    float2 atlasUv = (cell + uv) * invGridRes;
+
+    // Important: gradients must be computed in-cell; do not let integer cell offsets affect mip selection.
+    return _Impostors_Atlas.SampleGrad(bilinear_clamp_s, atlasUv, uvGradX * invGridRes, uvGradY * invGridRes);
+}
 
+// Billboard vertex transformation for impostors
+void impostor_vert(float4 vertexOS, inout float3 worldPos) {
     float3 center = mul(unity_ObjectToWorld, float4(0,0,0,1)).xyz;
-    o.centerPos = center;
+
     float3 scale = float3(
         length(unity_ObjectToWorld._m00_m10_m20),
         length(unity_ObjectToWorld._m01_m11_m21),
         length(unity_ObjectToWorld._m02_m12_m22));
 
-#ifdef IMPOSTOR_SHADOW_PASS
-    float3 camPos = _ImpostorMainCameraPos;
+#ifdef SHADOW_CASTER_PASS
+    float3 camPos = _Impostors_Main_Camera_Pos;
 #else
     float3 camPos = _WorldSpaceCameraPos;
 #endif
@@ -128,56 +102,35 @@ v2f vert(appdata v) {
     float3 viewWS = normalize(camPos - center);
     float3 right, up;
     BillboardBasis(viewWS, right, up);
-    float3 worldPos = center + v.vertex.x * right * scale.x + v.vertex.y * up * scale.y;
-    o.worldPos = worldPos;
-
-#ifdef IMPOSTOR_SHADOW_PASS
-    v.vertex = mul(unity_WorldToObject, float4(worldPos, 1));
-    v.normal = -viewWS;
-    TRANSFER_SHADOW_CASTER_NORMALOFFSET(o)
-#else
-    o.pos = mul(UNITY_MATRIX_VP, float4(worldPos, 1));
-    UNITY_TRANSFER_FOG(o, o.pos);
-#endif
-
-    return o;
+    worldPos = center + vertexOS.x * right * scale.x + vertexOS.y * up * scale.y;
 }
 
-// General purpose ray-sphere intersection.
-bool RaySphereIntersect(float3 ro, float3 rayDir, float3 origin, float radius) {
-    float3 originToRo = ro - origin;
-    float b = dot(originToRo, rayDir);
-    float c = dot(originToRo, originToRo) - radius * radius;
-    return (b * b - c) >= 0.0;
-}
+// Sample impostor atlas with view-dependent blending
+float4 impostor_frag(float3 worldPos) {
+    // Calculate center in fragment shader to avoid extra interpolator
+    float3 center = mul(unity_ObjectToWorld, float4(0,0,0,1)).xyz;
 
-float4 frag(v2f i) : SV_Target {
     // Sphere culling first
-    float3 viewDir = normalize(i.worldPos - _WorldSpaceCameraPos);
-    bool didIntersect = RaySphereIntersect(_WorldSpaceCameraPos, viewDir, i.centerPos, _SphereRadius);
-    clip(didIntersect - 0.5);
-
-    // Camera position for grid computation (matches billboard orientation)
-#ifdef IMPOSTOR_SHADOW_PASS
-    float3 camPos = _ImpostorMainCameraPos;
+#ifdef SHADOW_CASTER_PASS
+    float3 camPos = _Impostors_Main_Camera_Pos;
 #else
     float3 camPos = _WorldSpaceCameraPos;
 #endif
-    float3 center = i.centerPos;
+    float3 viewDir = normalize(worldPos - camPos);
+    bool didIntersect = RaySphereIntersect(camPos, viewDir, center, _Impostors_Sphere_Radius);
+    clip(didIntersect - 0.5);
 
     // For lattice lookup, use the camera-to-impostor-center direction (matches billboard orientation).
-    // Using the per-fragment view ray (camera→quad point) causes the selected lattice points/weights
-    // to vary across the billboard, which reads as "not smooth" while moving around the impostor.
     float3x3 worldToObject = (float3x3)unity_WorldToObject;
     float3 viewOS = normalize(mul(worldToObject, normalize(camPos - center)));
 
     // Get continuous grid position and find the 4 frames
-    float gridRes = (float)_GridResolution;
+    float gridRes = (float)_Impostors_Grid_Resolution;
     float2 grid = GridFromDir(viewOS, gridRes);
     float2 gridFloor = floor(grid);
     float2 gridFrac = frac(grid);
 
-    // Branchless barycentric blend weights (avoids discontinuities along triangle/cell boundaries).
+    // Branchless barycentric blend weights
     float4 bw = GridCellBarycentric4(gridFrac);
 
     // Frame cells (square corners)
@@ -194,7 +147,7 @@ float4 frag(v2f i) : SV_Target {
 
     // Compute virtual plane UVs for all 4 frames
     float3 pivotToCamOS = mul(worldToObject, camPos - center);
-    float3 vertexPosOS = mul(worldToObject, i.worldPos - center);
+    float3 vertexPosOS = mul(worldToObject, worldPos - center);
     float3 vertexToCamOS = pivotToCamOS - vertexPosOS;
 
     float2 uv00 = VirtualPlaneUV(dir00, pivotToCamOS, vertexToCamOS);
@@ -209,19 +162,13 @@ float4 frag(v2f i) : SV_Target {
     float4 s11 = SampleAtlasGrad(uv11, cell11, ddx(uv11), ddy(uv11));
     float4 col = s00 * bw.x + s01 * bw.y + s10 * bw.z + s11 * bw.w;
 
-#ifndef IMPOSTOR_SHADOW_PASS
-    if (_DebugMode > 0.5)
+    if (_Impostors_Debug_Mode > 0.5)
         return float4(bw.yz, 0, 1);
-#endif
 
-    col *= _Color;
-    clip(col.a - _Cutoff);
-#ifdef IMPOSTOR_SHADOW_PASS
-    SHADOW_CASTER_FRAGMENT(i)
-#else
-    UNITY_APPLY_FOG(i.fogCoord, col);
+    clip(col.a - _Impostors_Cutoff);
     return col;
-#endif
 }
 
-#endif
+#endif  // _IMPOSTORS
+
+#endif  // __IMPOSTOR_INC